View of The effect of nitrogen fertilization on the humification of the peat in cultivated Sphagnum bogs

THE EFFECT

^OF

NITROGEN FERTILIZATION

^ON

THE HUMIFICATION OF THE PEAT IN CULTIVATED

SPHAGNUM BOGS

Yrjö Pessi

Societyof^Peat Cultivation,ExperimentalStation Leteensuo

Received January 18, 1962

In a previous publication the author has reported ^his studies on the volume weight of^the organic matter ^{in the} plough layer of cultivated peat lands (4). The investigation revealed, among otherthings, that the volume weight ^{of the} organic matter^{in the} plough layer^was higherin the cultivatedfields which^{had been} given fertilizers or soil improving agents than in the unfertilized soils and those without addition of ^soil improving agents. ^In connection with cultivation, plant residues and root substances ^{are added} to ^{the soil} and ^the peat of cultivated bog areas is therefore less unadulterated than that of uncultivated bogs. It is obvious, however, that the differencesinvolume weight observed on cultivated bog areas are certainly to alarge extent due to changes ^{in the}structureof^thepeat itself.^Asafairly strong correlation is^known to exists between thevolume weight ^{and the} degree of humi- fication ^of peat (1, 5), ^{it is} thought justifiable to conclude ^{that both} fertilization and soil improvement actin favour of the humification ^ofpeat. ^{In the} said investi- gation, inferences concerning the effects of various nutrients could only be ^made with respect to potassium fertilization, which ^was found to have ^an increasing effect^onthevolume weightof theorganic matterⁱⁿfen peatⁱⁿthe tests at^Leteensuo.

As the mobilization of nitrogen is quiteminimal in Sphagnum peat, which is the reason why nitrogen fertilization occupies a key position ^{in the} cultivation ^of Sphagnum bogs, ^for instance, ^it is to ^be expected ^thatnitrogen fertilization also hasits significance

.with

^{respect to the} activity ^of micro-organisms^{and thus}to the humification of Sphagnum peat. This questionwas studiedinsome detail inconnec- tion with a nitrogen fertilization test at Leteensuo, ^the results of which will be

described^{in the}presentpaper. In theinvestigation ^{the volume}weight^{of the}organic matter in the plough layer ^was determined ^{in the} same manner as in the author’s earlier investigation (4). Differences ⁱⁿ volume weight ^{have been} interpreted as showing^also adifference in degree^ofhumification ofthepeat onthe strength of^the correlation between thetwo quantities. The soil samples ^were taken in^{the summer} of ^1960. They ^were treated in the ^manner described in ^aprevious publication (3).

42

Test _area and results

The test ^{area was} cleared for cultivation in 1921. The peat on the area was poorly humified Sphagnum

fuscum

^{peat.The testwas startedin 1923,inwhichyear}

claywas spreadon the fieldassoil improving agent at^therateof 300

m ^{3 per}

^hectare.

Thearea waslimedin the sameyear(with 4000kg slaked lime per hectare).

The results from the test up to 1959 have been described before (2). The said publication also contains detailed information on the test. The test was originally a combined nitrogen fertilization ^and stable ^manure application test. One of two strips had received stable^{manure in a} quantity of²⁰tons per hectare in 1923—24, 30.6 tons per hectare in 1929, ³⁰ tons per hectare in 1930 and 30 tons per ^hectare in 1933.The same fertilizer treatment was applied to both strips, namely: 0, PK, NPK, 2NPK and 3NPK (N =l5kgN,P ⁼ 40kg ^P 20₅^{, K = 100}kg ^K₂O, all per hectare). In 1949 thefertilizing planwaschangedsothat the strip previously treated with stable ^{manure was} given ^the fertilizations ^0, PK, 3NPK, ^{6NPK and} 9NPK, respectively. These artificial fertilizers ^were given annually except in the year 1948.

Calcium nitrate, superphosphate ^and potassium salt ^were used. As the objects of the investigations weretaken the treatments PK, NPK, 2NPKand 3NPK without stablemanure. These treatmentshave been the _same since^the beginning^{of the} test.

The volume weight of the peat was determined separately ^for each replicate.

Theresults were subjected to ananalysis ^ofvariance.

Volume weight of^theash-free, dry peat in the plough layer found in the differenttreatments.

Fertilization Volumeweight Increment

PK 0.262

NPK 0.288 +0.026

2NPK 0.288 +0.026

3NPK 0.316 +0.054

F-value 5.39*

The results of the investigation presented in the accompanying table reveal that the volume weight of^the ash-free, dry peat washigher^{in the}treatments ^with nitrogen fertilization than in the PK treatment. This ^seemsto justify^theconclusion thatnitrogen fertilization has been conducive to greater microbial activity ^{and has} thus furthered ^the humification of the peat.

Summary

The paperis areport on the volume weights of the ash-free, dry peat on the cultivated Sphagnum bog at Leteensuo found in connection with different degrees ofnitrogen fertilization.The ^volumeweight attained higher values under nitrogen fertilization than in thetreatments^withmerepotassium ^andphosphate fertilization.

As the volumeweight ^of peat also increases ^withincreasing humification, ^{the con-} clusion ^was drawn from the results that nitrogen fertilization has favoured ^the humification of Sphagnum peat.

43

REFERENCES

(1) Kaila, ^A. 1956. Determination of ^the degreeof humification inpeat samples. ^Selostus; Turpeen maatumisasteen määrittäminen. Maatal.tiet.aikak. ^28: 18—35.

(2) Pessi, Y. 1960.Fertilization of Sphagnumbogs,onthe basis of certain field experimentsat Leteensuo.

Selostus: Rahkasuon lannoitus eräiden Leteensuon kokeiden perusteella. Ibid. 32; 144 157.

(3) —1961. The ash content of ^theplough layer^ofpeat lands cultivated by different methods.

Selostus: Viljeltyjen turvemaidenmuokkauskerroksentuhkapitoisuudesta.Ibid.33: 215—222.

(4) —1961. The volumeweightof theorganic matterin theplough layerofpeatlands cultivated by different methods. Selostus: Viljeltyjen turvemaiden muokkauskerroksen orgaanisen aineen tilavuuspainosta. Ibid. 33: 248 255.

(5) ^Pjatvtshenko, H. 1958.Turpeenmaatumisasteen määrittely (Finnish translation).

TYPPILANNOITUKSEN VAIKUTUKSESTA RAHKATURPEEN HUMIFIOITUMISEEN

Yrjö Pessi

Suoviljelysyhdistys,Leteensuon koeasema

Tutkimuksessa onselostettu Leteensuon rahkasuoviljelyksen muokkauskerroksen tuhkattoman ja kuivan turpeen tilavuuspainoja eri suuruisten salpietarilannoitusten yhteydessä. Kun salpietari- lannoitus on annettuvuosittain^lähesneljänkymmenen ^vuodenajanfosfori- ja kalilannoituksen lisäksi, on muokkauskerroksen turpeentilavuuspaino muodostunut suuremmaksi kuin pelkän^fosfori- ja ^kali- lannoituksen johdosta. ^Kunturpeen tilavuuspainosuurenee turpeen maatuessa, tehtiin^tulostenperus- teella päätelmä, ^ettätyppilannoitus edistäärahkaturpeen humifioitumista.